A method and a device for operation in an indoor CDMR telecommunications system are referred to in European published patent application Ser. No. 0 865 172, in which two or more wireless communications systems are operated superimposed. One of the two systems is an indoor system and the other is an outdoor system. The indoor system monitors the operation of the outdoor system and detects which part of the available radio resources are sometimes not used or are interference-free in the outdoor system. The indoor system dynamically selects an unused outdoor channel for indoor operation. The indoor radio traffic is divided into TDD time slots, which include the time slots for monitoring the existing radio connections on other outdoor channels, so that rapid changes are possible in accordance with changing traffic and changing interference conditions. A threshold value comparison is performed during the selection of the channels.
In mobile radio systems of the third generation, for example in accordance with the GSM standard (Global System for Mobile Communications) or the UMTS standard (Universal Mobile Telecommunication System) or the like, two concepts (or modes) may be provided for transmitting signals via an air interface between a base station and a mobile station, depending on the transmission resource used. If various frequency bands are provided as a transmission resource, an FDD mode (Frequency Division Duplex) may be used, in which two different frequency bands are used to transmit the signals from the mobile station to the base station in the uplink transmission direction and from the base station to the mobile station in the downlink transmission direction. If time slots are used as a transmission resource, the TDD mode (Time Division Duplex) may be used, in which different time slots are used for the uplink transmission direction and the downlink transmission direction, while using the same frequency band. Further channel separation is possible for both modes in this case.
However, in uncoordinated operation the base stations may not be linked via a higher-order system, so that coordinated code assignment may not be possible. Such operation may be advisable, for example, for the home sector with cordless telephones, in which, under certain circumstances, many individual base stations may be operated independently from one another. In this case, the code assignment may not be coordinated. Therefore, only one base station may be active per transmission resource, for example, per time slot or per frequency band, but even using multiple different codes for this purpose. This transmission resource may be occupied for a neighboring base station; since the station may not know the codes used. A power measurement may permit the neighboring base station to detect whether a transmission resource is occupied. If so, the neighboring base station may substitute other transmission resources, for example, other time slots or frequency bands.